Conventionally, as such a kind of the master cylinder apparatus, there is a known master cylinder apparatus in a vehicle brake system for controlling a brake fluid pressure applied to wheel brakes of a vehicle (automobile) (for example, see Patent document 1).
The vehicle brake device includes a base including a master cylinder and fluid passages therein and a solenoid valve for opening and closing the fluid passages, and parts such as a pressure sensor for detecting a magnitude of the brake fluid pressure, etc. are attached to the base.